The answer to 'heat exchanger not cooling' is that a malfunctioning or damaged heat exchanger is a common cause. Symptoms may include the unit not blowing cold air, higher-than-normal energy bills, and strange noises or smells from the HVAC system. Solutions can range from cleaning or repairing the heat exchanger to replacing the entire unit, depending on the severity of the issue.
If the heat exchanger is the problem, it's generally best to call a professional HVAC technician to diagnose and fix the issue. Attempting to repair or replace a heat exchanger yourself can be dangerous, as it involves working with high-voltage electrical components and potentially hazardous materials like refrigerant. A qualified technician will have the proper tools, knowledge, and safety equipment to handle the job safely and effectively.